After water is used in pulp and papermaking processes, it is carefully treated and returned back to the natural water system. Waste water treatment is an important part of Stora Enso’s water management, and a lot of attention has been paid to waste water treatment at the mills over the years.

Two examples from Sweden illustrate what Stora Enso’s mills are doing to further improve the efficiency of their waste water treatment plants.

Nymölla Mill is increasing the aeration capacity of the activated sludge process at the mill’s waste water treatment plant. The increased oxygen content in the aeration basin will improve the settling of sludge in the clarifiers, and increase the uptake of phosphorus and nitrogen by microorganisms, resulting in lower discharges into the sea. The new aeration equipment will be taken in operation in the spring of 2005.

Kvarnsveden Mill is increasing the capacity of its waste water treatment plant in order to meet the mill’s future needs in conjunction with the investment in a new paper machine and the increased production of mechanical pulp. The upgrading of the waste water treatment plant will involve switching from a trickling filter system to a Moving Bed Biofilm Reactor (MBBR) system, and the installation of a new flotation stage to increase sludge separation capacity. The upgraded plant will be taken into operation during 2005.